Gene therapy has the potential for treating various lung diseases. However, its clinical use is unrealized because of the lack of a safe and efficient gene delivery technology. Current cationic polymers have low transfection efficiencies and are toxic to the lungs due to excessive charges and non-biodegradable nature. Also, unmethylated CpG groups that exist in plasmid DNA could trigger an inflammatory response when it is delivered as complex with a carrier. We hypothesize that a safer and more efficient nonviral gene delivery system can be derived by designing multifunctional, more biocompatable carriers and gene sequences that have minimal size and low content of unmethylated CpG groups. We described here a new synthetic route that led to a class of polyhydroxylalkyleneamine with adjustable charge densities, variable spacing groups and a high content of hindered nitrogens with lowered pKa. Cell and airway transfection using DNA/polymer complexes showed several fold higher transfection activity than those using polyethylenimine/DNA complexes. The new polymers showed much reduced toxicity than polyethylenimine. More importantly, reducible disulfide bonds and hydrophobic groups can be added to backbones to make these polymers biodegradable and more potent, respectively. We propose to identify most active and least toxic polymers by adjusting polymer properties such as DNA condensation, membrane activity and biodegradability. We also propose to better understand this new gene delivery system through detailed characterization of physicochemical properties, mechanism of transfection and metabolism profiles of these polymers in vitro and in vivo. In addition, polymer/DNA complexes dressed with antibodies specific to ICAM-1 will be tested for their effect to reduce the surface charges of the polymer/DNA complex and to trigger specific cell uptake via receptor-mediated endocytosis. Lastly, a DNA fragment containing a small-sized functional gene expression cassette with minimal unmethylated CpG contents will be tested in vivo to reduce inflammation response. Combining these innovations, we will establish a safe and efficient non-viral gene delivery system suitable for the airway delivery and potential applications for other organs. [unreadable] [unreadable]